I think the draw of pacman is that it's really simple. (Actually that's the draw of Archlinux overall.) Pacman is fast, useful, and you can learn its feature set in ten minutes. Apt-Get is considerably more complex by comparison. Especially, and I think this is where pacman really shines, is making new packages. All it takes to build a pacman package is simple PKGBUILD file. This is analogous to a Gentoo ebuild but much simpler.

I think some of the other comments have addressed this, but I'll comment on the rollback issue.

If you just want to rollback you can download the current package if it's not in your cache. If you want and rollback to previous version, there's downgrade and the Arch Rollback Machine https://wiki.archlinux.org/index.php/Downgrade#ARM

Really, though, it's never been an issue for me. I've yet to encounter a situation where I nuke my cache and don't have rollback packages available. It boils down to a management issue. If you are nuking your package cache, I assume you are smart enough to have determined your system is running correctly first. There are cases where you might still want to rollback after clearing your package cache, so there is ARM.

Personally, if I ever hit that situation (absolute worst case scenario) I have backups and can reinstall an Arch system in minutes. Haven't had the need yet.

The only time it backfired at me is when the package you want to rollback to is not in your cache, and basically the only time it happens is for the version installed during the install phase: the installer does not copy the package from the install medium to the target package cache, as it uses it straight from the medium.

You still can't rollback without either having the package in your cache, or going to the source repo and grabbing the old PKGBUILD

The great thing is there are other package managers built on top to be more friendly such as yaourt. So if you think pacman is too primitive then you have options.